As a technique of obtaining bloodstream information inside a patient body, fluoroscopic imaging with the use of contrast agent and an X-ray diagnostic apparatus is known. As an example of fluoroscopic imaging, DSA (Digital Subtraction Angiography) images are generated by time-sequentially imaging the same region of a patient using an X-ray diagnostic apparatus before and after administration of contrast agent.
Specifically, subtraction images corresponding to respective time phases obtained by subtracting a mask image from a contrast image of each time phase imaged after administration of contrast agent are defined as DSA images. The above-described mask image means an X-ray image imaged before administration of contrast agent used as a reference, and the above-described contrast image means an X-ray image in which contrast agent is depicted. Since blood vessels dyed by contrast agent are selectively depicted in DSA images by eliminating shade and shadow unnecessary for observing blood vessels, DSA images are useful for diagnosis of blood vessels.
When a doctor diagnoses a blood vessel disease such as cerebral arteriovenous malformation and dural arteriovenous fistula, a blood vessel image useful for diagnosis cannot be obtained only from DSA images in some cases. To be concrete, it becomes difficult in some cases to specify or distinguish a blood vessel through which contrast agent flows into a lesion area.